Mathematical models to describe the growth curves of white-egg layers

The aim of this study was to compare mathematical models describing growth curves of white-egg layers at different population densities. To fit the models, 4,000 growing white-egg layers were utilized. The experimental design was completely randomized, with population densities of 71, 68, 65, 62, and 59 birds per cage in the starter phase and 19, 17, 15, 13, and 11 birds per cage in the grower phase, with 10 replicates each. Birds were weighed weekly to determine the average body weight and the weight gain. Gompertz and Logistic models were utilized to estimate their growth. The data analysis was carried out using the PROC NLMIXED procedure of the SAS® statistical computer software to estimate the parameters of the equation because mixed models were employed. The mean squared error, the coefficient of determination, and Akaike’s information criterion were used to evaluate the quality of fit of the models. The studied models converged for the description of the growth of the birds at the different densities studied, showing that they were appropriate for estimating the growth of white-egg layers housed at different population densities. The Gompertz model showed a better fit than the Logistic model

Digestibilidade da ração de frangos de corte suplementados com probióticos e antibiótico Digestibility of broiler chickens diet supplemented with probiotics and antibiotics

O objetivo deste experimento foi avaliar a digestibilidade da ração de frangos de corte a qual continha ou não antibiótico e probióticos na fase inicial (um a 20 dias) e na fase final (21-40 dias). As aves foram distribuídas em um delineamento inteiramente casualizado com quatro tratamentos: Tratamento 1- Dieta Testemunha; Tratamento 2 - Dieta Testemunha + 0,02 % de probiótico 1 (Calsporin 10®), Tratamento 3 - Dieta Testemunha + 2,0% na fase inicial e 0,63% na fase final de probiótico 2 (Estibion aves®); Tratamento 4 - Dieta Testemunha + 0,013% de antibiótico (Bacitracina de Zinco®) e 5 repetições de 10 e 8 aves por unidade experimental por fase, respectivamente. Os pintos foram criados em gaiolas de metabolismo. Os resultados demonstram que a digestibilidade de matéria seca, nitrogênio e energia metabolizável aparente não foi afetada pela suplementação de antibiótico e probióticos na dieta de frangos de corte.<br>The objective of this experiment was to evaluate the diets digestibility in broiler chickens with and without antibiotic and probiotics, in the initial phase (one to 20 days) and finish phase (21 to 40 days). Chickens distributed in a completely randomized design were used in four treatments: Treatment 1- Control diet; Treatment 2 - Control diet + 0.02% probiotic 1 (Calsporin 10®), Treatment 3 - Control diet + 2.0% initial phase and 0.63% finish phase probiotic 2 (Estibion aves®); Treatment 4 - Control diet + 0.013% of antibiotic (Bacitracina de Zinco®), and five repetitions, with ten and eight birds, respectively, were used in each experimental unit, which were kept in metabolism cages. The results demonstrate that the digestibility of dry matter, nitrogen and apparent metabolized energy were not affected by the supplementation of antibiotic and probiotics in the broiler chickens diet

Digestible lysine for broiler chickens with lower genetic potential grown on free-range system

ABSTRACT Determining the actual lysine requirement is crucial as it is an essential amino acid and plays animportant role in the metabolism of broilers. In addition, it is the second limiting amino acid for broilers fed with rations formulated basedon corn and soybean meal. The aim of this study was to determine the digestible lysine requirement for male broilers with lower genetic potential for growth in a semi-confined system as well as to evaluate the effects of different values of digestible lysine on performance and carcass characteristics. A total of 300 broiler chickensfrom a commercial lineage EMBRAPA 041 were used with an average initial weight of 987 g. The broilers were distributed into 20 experimental units in a completely randomized design with five treatments (0.586; 0.746; 0.906; 1.066, and 1.226% digestible lysine), four replicates and 15 broilers per experimental unit.In both periods, there were linear effect of digestible lysine values on the lysine intake and lysine utilization efficiency and quadratic effect on final body weight, weight gain and feed: gain ratio.There was a quadratic effect on the absolute weight of carcasses, breast, thigh + drumstick and income gizzard.For rearing of male broilers with lesser genetic growth potential reared in semi-confinement, rations with 1.040% and 1.103% digestible lysine can be recommended for maximum weight gain in periods from 35 to 70 and 35 to 84 days of age, respectively